CN103534103A - Pneumatic tire - Google Patents

Abstract

A pneumatic tire (1), comprising an inner side of a carcass (6) erected between a pair of bead portions (4), and an airtight layer (9); The first layer (PL1), the second layer (PL2, PL3) arranged in contact with the rubber layer of the carcass layer (6); the first layer (PL1) is a thermoplastic elastomer composition, containing: containing styrene-isobutylene- Styrene block copolymers, thermoplastic elastomers of at least one of SIBS modified copolymers whose styrene block portions are modified by acid chlorides or acid anhydrides having unsaturated bonds, and ultraviolet absorbers or antioxidants At least any one; the second layer (PL2, PL3) is a thermoplastic elastomer composition containing at least any one of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer.

Description

pneumatic tire

technical field

The present invention relates to a pneumatic tire provided with an inner liner, and in particular, relates to an air inflation system that improves durability and weather resistance while suppressing the growth of flex cracks in the inner liner caused by repeated flexural deformation during tire running. tire.

Background technique

In recent years, due to the strong social demand for low fuel consumption of vehicles, the weight reduction of tires is being pursued. Among tire components, for reducing the amount of air leakage from the inside of the pneumatic tire to the outside (the drop in air internal pressure) ), improving the air permeability resistance of the inner liner, and also reducing weight.

Currently, the rubber composition for an inner liner improves the air permeation resistance of the tire by using, for example, a rubber composition mainly composed of butyl rubber containing 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. In addition, the rubber compound mainly composed of butyl rubber contains about 1% by mass of isoprene in addition to butene, which is combined with sulfur, vulcanization accelerator, and zinc oxide to enable crosslinking between rubber molecules. The above-mentioned butyl-based rubber generally requires a thickness of 0.6 to 1.0 mm for passenger car tires, and about 1.0 to 2.0 mm for truck and bus tires. In order to reduce the weight of tires, butyl-based rubber is required. A polymer with good air permeability resistance and can reduce the thickness of the inner liner.

Conventionally, in order to reduce the weight of tires, films made of thermoplastic resin-containing materials have been proposed instead of the above-mentioned rubber compositions. However, if exposed to the outdoors during tire transportation or store display at the sales store, it will deteriorate due to the ultraviolet rays of the sun, and the deterioration of the thermoplastic elastomer will cause cracks, which will give an impression of poor interior appearance. In addition, since the internal space of a pneumatic tire is filled with air during use, oxygen in the air permeates into the interior of tire components, and oxidation over time adversely affects the durability of the pneumatic tire. In particular, if the inner liner is cracked, it will give users an impression of poor interior appearance. In addition, the gas barrier property of the part deteriorates, and the tire internal pressure decreases.

In addition, the inner liner exerts a large shear strain on the vicinity of the tire shoulder when the tire is running. When a material containing a thermoplastic resin is used as the inner liner, there is a problem that the adhesive interface between the inner liner and the carcass is likely to be peeled off due to the shear strain, resulting in a tire blowout.

In addition, in order to reduce the weight of the inner liner, a technique using a thermoplastic elastomer material has also been proposed. However, it is known that for an inner liner thinner than butyl rubber or a material exhibiting higher air permeability resistance, the vulcanized adhesion ratio between the insulation rubber or the ply rubber adjacent to the inner liner is Butyl rubber has a poor airtight layer.

If the vulcanized adhesive force of the inner liner is low, air will be mixed between the inner liner and the isolation rubber or carcass rubber, and a small balloon-like substance will appear, which is the so-called air intake phenomenon. There are many small markings on the inner side of the tire. In addition to giving the user an impression of poor appearance, the air-intake point will be the starting point during driving, peeling will occur, cracks will occur in the inner liner, and the internal pressure of the tire will drop.

In Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-298986 ), titanium oxide is added to a mixture of butyl-based rubber and nylon resin in order to prevent ultraviolet degradation. However, in addition to ultraviolet degradation, there is a problem of degradation by radicals of the nylon resin due to flexural fatigue, and a decrease in durability.

In addition, in Patent Document 2 (WO2007/116983 A), the surface layer is provided with a light-shielding layer in which carbon black is added to a mold release agent in order to prevent ultraviolet degradation of the thermoplastic elastomer layer. However, due to the variation in the process of applying the release agent, it may not be uniformly applied to the inner surface of the tire, or if it is scratched by the hands of the operator or user or other reasons during the process, it will not be able to function as a light-shielding layer. There is a problem of decreased durability due to UV deterioration.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2009-298986

Patent document 2: WO2007/116983 publication

Contents of the invention

The present invention relates to a pneumatic tire provided with an inner liner, which suppresses the growth of flex cracks in the inner liner due to repeated flexural deformation during tire running, improves durability, and improves weather resistance.

The present invention relates to a pneumatic tire comprising an inner liner on the tire inner side of a carcass stretched between a pair of bead portions; The second layer is composed of the rubber layer arranged in contact with each other; the first layer is a thermoplastic elastomer composition, containing: a styrene-isobutylene-styrene block copolymer, and its styrene block is partially unsaturated The thermoplastic elastomer of at least any one of the acid chloride or acid anhydride modified SIBS modified copolymer of the bond, and at least one of the ultraviolet absorber and antioxidant; the second layer is a thermoplastic elastomer composition containing benzene At least any one of an ethylene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer.

In the pneumatic tire of the present invention, it is preferable that at least one of an ultraviolet absorber and an antioxidant is added to the first layer in an amount of 0.5% by mass to 40% by mass of the thermoplastic elastomer component. In addition, it is preferable that a SIBS modified copolymer is added to any one of the thermoplastic elastomer compositions of the first layer and the second layer in an amount of 5% by mass to 100% by mass of the thermoplastic elastomer component. %.

In the pneumatic tire of the present invention, it is preferable that the thermoplastic elastomer composition of the first layer is a mixture of a styrene-isobutylene-styrene block copolymer and a SIBS modified copolymer. In addition, it is preferable that a tackifier is added to any one of the thermoplastic elastomer compositions of the first layer and the second layer.

A thermoplastic elastomer composition containing a styrene-isobutylene-styrene block copolymer tends to deteriorate in the wavelength range of ultraviolet light of 290 nm or more. Therefore, by adding an ultraviolet absorber to the thermoplastic elastomer composition, it absorbs light near 320nm to 350nm, which is most likely to deteriorate, and converts it into molecular vibration energy or thermal energy, thereby protecting the thermoplastic elastomer under ultraviolet rays. function. Here, a photostabilizer is also included in the ultraviolet absorber.

In addition, the thermoplastic elastomer will generate free radicals due to flex fatigue during tire running, and the free radicals will induce chain deterioration of the main chain, resulting in cracks and destruction of the inner liner made of the thermoplastic elastomer composition. Then, by adding an antioxidant, free radicals generated due to flex fatigue are captured to prevent deterioration. Here, oxygen absorbing agents are also included in antioxidants.

Description of drawings

[ Fig. 1 ] is a schematic sectional view of the right half of the pneumatic tire of the present invention.

[ Fig. 2 ] is a schematic cross-sectional view showing a bonded state of an inner liner and a carcass.

[ Fig. 3 ] is a schematic cross-sectional view showing a bonded state of an inner liner and a carcass.

[ Fig. 4 ] is a schematic cross-sectional view showing a bonded state of an inner liner and a carcass.

[ Fig. 5 ] is a schematic cross-sectional view showing a bonded state of an inner liner and a carcass.

Symbol Description

1 pneumatic tire, 2 tread portion, 3 sidewall portion, 4 bead portion, 5 bead core, 6 ply, 7 belt, 8 apex, 9 inner liner, PL polymer laminate, PL1 SIBS layer, PL2 SIS layer, PL3 SIB layer.

Detailed ways

〈Structure of a tire〉

The pneumatic tire provided with the airtight layer inside the tire of this invention is demonstrated based on drawing. Fig. 1 is a schematic sectional view of the right half of a pneumatic tire. In the drawing, a pneumatic tire 1 has a tread portion 2 , and sidewall portions 3 and bead portions 4 formed into ring shapes from both ends of the tread portion. In addition, a bead core 5 is embedded in the bead portion 4 . In addition, a carcass 6 spanning from one bead portion 4 to the other bead portion, both ends of which are folded back and locked around the bead core 5 , and outside the crown portion of the carcass 6 , at least The belt layer 7 composed of two cords.

The belt layer 7 is usually two cords made of steel cords or aramid fiber cords, and the cords are usually arranged to cross each other at an angle of 5 to 30° with respect to the tire circumferential direction. In addition, top rubber layers are provided on the outer sides of both ends of the belt layer, which can reduce peeling of both ends of the belt layer. In addition, the ply is made of organic fiber such as polyester, nylon, or aramid. The cords are arranged at approximately 90° in the tire circumferential direction. The apex 8 extending in the direction. In addition, an inner liner 9 spanning from one bead portion 4 to the other bead portion 4 is provided on the inner side in the tire radial direction of the carcass layer 6 .

<airtight layer>

The inner liner in the present invention is composed of a first layer composed of a thermoplastic elastomer composition disposed inside the tire and a second layer composed of a thermoplastic elastomer composition disposed in contact with the rubber layer of the carcass. constitute. Here, the thermoplastic elastomer composition refers to a composition containing a thermoplastic elastomer or a rubber component as a polymer component. However, rubber components added as additives, such as polyisobutylene, are not included in the thermoplastic elastomer component in the present invention.

〈Level 1〉

In the present invention, the first layer is formed of a thermoplastic elastomer composition containing a styrene-isobutylene-styrene block copolymer (hereinafter also referred to as "SIBS") and its styrene block At least any one of styrene-isobutylene-styrene block copolymers (hereinafter also referred to as “SIBS-modified copolymers”) partially modified with acid chlorides or acid anhydrides having unsaturated bonds.

<Styrene-isobutylene-styrene block copolymer (SIBS)>

The molecular chain of SIBS contains isobutylene block, so its polymer film has good resistance to air permeability. Therefore, when SIBS is used for the inner liner, a pneumatic tire having good air permeability resistance can be obtained. In addition, since the molecular structure of SIBS is saturated except for the aromatic unit, oxidation deterioration is suppressed.

The molecular weight of SIBS is preferably 50,000 to 400,000 as measured by GPC from the viewpoint of fluidity, molding process, rubber elasticity, and the like. When the weight average molecular weight is less than 50,000, there is a possibility that tensile strength and tensile elongation may decrease, and when it exceeds 400,000, extrusion processability may be deteriorated. SIBS is preferably 10 to 30% by mass of the styrene component content in SIBS from the viewpoint of better air permeability resistance and durability.

In SIBS, the degree of polymerization of each block in the molecular chain is preferably about 10,000 to 150,000 for isobutylene units, and about 5,000 to 30,000 for styrene units. SIBS can be produced by a general living cationic polymerization method of vinyl compounds. For example, Japanese Patent Laid-Open No. 62-48704 and Japanese Patent Laid-Open No. 64-62308 disclose living cationic polymerization of isobutylene and other vinyl compounds.

<SIBS modified copolymer>

The first layer is a composition containing 10% by mass to 100% by mass of the SIBS modified copolymer as a thermoplastic elastomer component. Here, the SIBS modified copolymer is a substance in which the styrene block part of styrene-isobutylene-styrene block copolymer (SIBS) is modified by an acid chloride or anhydride having an unsaturated bond, and its molecular chain contains the following Chemical structure of formula (1).

[chemical 1]

In the formula (1), n is an integer, and R ₁ is a monovalent organic group with a functional group.

The acid chloride having an unsaturated bond used in the modification of the present invention refers to, for example, methacryloyl chloride, methacryloyl bromide, methacryloyl iodide, acryloyl chloride, acryloyl bromide, acryloyl iodide, Crotonyl chloride and crotonyl bromide. Particularly suitable are methacryloyl chloride, acryloyl chloride.

In addition, acid anhydride refers to, for example, acetic anhydride, maleic anhydride, phthalic anhydride, etc., but acetic anhydride is particularly suitable. These compounds may be used in combination of two or more. Since an unsaturated group is introduced into SIBS through related modification, it can be crosslinked using a crosslinking agent.

As mentioned above, the mixing amount of styrene-isobutylene-styrene block copolymer modified by acid chloride and acid anhydride having unsaturated bonds is 10-100% by mass of the thermoplastic elastomer component, preferably 30-100% by mass. 100% by mass range. If the blending amount of the SIBS modified copolymer is less than 10% by mass of the thermoplastic elastomer component, the vulcanized adhesion with the second layer and the carcass rubber will be insufficient.

The content of acid chlorides and acid anhydrides having unsaturated bonds in the SIBS modified copolymer is 1% by weight or more, preferably 5% by weight or more and 30% by weight or less.

The cross-linking of the SIBS-modified copolymer can use a conventional method, for example, thermal cross-linking by heating or cross-linking by a cross-linking agent can be used. Here, as a crosslinking agent, organic peroxides such as dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl peroxide, ) hexane, etc.

The blending amount of the organic peroxide is preferably in the range of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer component.

In addition, in the thermoplastic elastomer composition of the present invention, polyfunctional vinyl monomers (such as divinylbenzene), triallyl cyanurate, or polyfunctional methacrylate monomers can be used in combination as crosslinking agents. Glycol Dimethacrylate, Diethylene Glycol Dimethacrylate, Triethylene Glycol Dimethacrylate, Polyethylene Glycol Dimethacrylate, Trimethylolpropane Trimethyl acrylate or allyl methacrylate), in this case, it can be expected to improve the flex cracking properties of the crosslinked composition.

Due to the isobutylene block of the SIBS modified copolymer, the film composed of the SIBS modified copolymer has good air permeability resistance. In addition, since the unsaturated group in the SIBS modified copolymer is introduced into the ISBS, it can be crosslinked by thermal crosslinking and crosslinking agent, which can improve the basic properties such as tensile strength, elongation at break and permanent strain, and at the same time improve Flex crack characteristics and air permeability resistance improve the characteristics as an inner liner.

When a polymer film composed of a thermoplastic elastomer composition containing a SIBS-modified copolymer is used as an inner liner to manufacture a pneumatic tire, air permeability resistance can be ensured. Therefore, it is unnecessary to use a halogenated rubber having a high specific gravity, such as halogenated butyl rubber, which has been conventionally used for imparting air permeation resistance, and even if it is used, the usage amount can be reduced. As a result, the weight of the tire can be reduced, and fuel efficiency can be improved.

The molecular weight of the SIBS-modified copolymer is not particularly limited, but it is preferably 50,000 to 400,000 in weight average molecular weight measured by GPC from the viewpoint of fluidity, molding process, rubber elasticity, and the like. If the weight average molecular weight is less than 50,000, there is a possibility that the tensile strength and tensile elongation may decrease, and if it exceeds 400,000, the extrusion processability may deteriorate, so it is not preferable. The content of the styrene component in SIBS is 10 to 30% by mass, preferably 14 to 23% by mass, from the viewpoint of better air permeability resistance and durability in the SIBS modified copolymer.

In this SIBS copolymer, the degree of polymerization of each block is preferably about 10,000 to 150,000 for isobutylene and about 5,000 to 30,000 for styrene from the viewpoint of rubber elasticity and handleability (liquid state when the degree of polymerization is less than 10,000).

<Manufacture of SIBS modified copolymer>

SIBS can be obtained by the living cationic polymerization method of general vinylic compounds. For example, Japanese Patent Laying-Open No. 62-48704 and Japanese Patent Laid-Open No. 64-62308 disclose that isobutylene can be polymerized with other vinyl compounds in active cationic polymerization. By using isobutylene and other compounds in vinyl compounds, Polyisobutylene-based block copolymers can be produced.

The production of the SIBS-modified copolymer can employ, for example, the following method. After charging the styrene-isobutylene-styrene block copolymer into the separation bottle, the inside of the polymerization vessel was replaced with nitrogen. Then add an organic solvent (for example, n-hexane and butyl chloride) dried through molecular sieves, and then add methacryloyl chloride. Finally, aluminum trichloride was added to the solution while stirring it to react. After starting the reaction for a certain period of time, a predetermined amount of water was added to the reaction solution and stirred to complete the reaction. The reaction solution is washed several times with a large amount of water, and then a large amount of methanol and acetone mixed solvent is slowly dropped to precipitate the polymer, and the obtained polymer is vacuum-dried to obtain. In addition, the production method of the SIBS modified copolymer is disclosed in Japanese Patent No. 4551005, for example.

<Thermoplastic elastomer composition containing SIBS modified copolymer>

The first layer is a thermoplastic elastomer composition mainly composed of SIBS modified copolymer. That is, the thermoplastic elastomer component contains 90% by mass or more of the SIBS-modified copolymer. Here, as the thermoplastic elastomer, styrene-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and the like can be suitably used.

A rubber component may be added to the thermoplastic elastomer composition of the first layer. By adding the rubber component, it is possible to impart unvulcanized adhesiveness to the adjacent carcass, and to improve the vulcanized adhesiveness to the carcass or insulation layer by vulcanization.

The rubber component preferably contains at least one member selected from the group consisting of natural rubber, isoprene rubber, chloroprene rubber, and butyl rubber. The mixing amount of the rubber component is preferably in the range of 5 to 75% by mass in the polymer component.

<Ultraviolet absorber>

In the present invention, an ultraviolet absorber is added to the elastomer composition. The ultraviolet absorber absorbs light in the ultraviolet region with a wavelength of 290 nm or more, and prevents deterioration of the molecular chain of the polymer compound. For example, benzophenone-based, salicylate-based, and benzotriazole-based ultraviolet absorbers absorb ultraviolet light near a wavelength of 320 nm to 350 nm, which is most likely to degrade polymer compounds. By converting light in this wavelength region into vibrational energy or thermal energy, it has the function of preventing the absorption of polymer compounds. In particular, benzotriazole-based ultraviolet absorbers can absorb ultraviolet light in a wide range. Here, ultraviolet absorbers are exemplified as follows.

[Benzotriazole UV Absorbers]

TINUVIN P/FL (manufactured by BASF, molecular weight 225, melting point 128-132°C, maximum absorption wavelength 341nm) (2-(2-hydroxy-benzotriazol-2-yl)-p-cresol)

TINUVIN234 (manufactured by BASF, molecular weight 447.6, melting point 137-141°C, maximum absorption wavelength 343 nm) (2-[2-hydroxy-3,5-bis(α,α'-dimethylbenzyl)phenyl]-2H -benzotriazole)

TINUVIN326/FL (manufactured by BASF, molecular weight 315.8, melting point 138-141°C, maximum absorption wavelength 353nm), Adekastab LA-36 (manufactured by ADEKA Corporation) (2-(2'-hydroxy-3'-tert-butyl-5 '-methylphenyl)-5-chlorobenzotriazole)

TINUVIN237 (manufactured by BASF, molecular weight 338.4, melting point 139-144°C, maximum absorption wavelength 359 nm) (2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl-)phenol)

TINUVIN328 (manufactured by BASF, molecular weight 351.5, melting point 80-88°C, maximum absorption wavelength 347nm) (2-(3,5-di-tert-amyl-2-hydroxyphenyl)benzotriazole)

TINUVIN329/FL (manufactured by BASF, molecular weight 323, melting point 103-105° C., maximum absorption wavelength 343 nm) (2-(2-hydroxy-benzotriazol-2-yl)-4-tert-octylphenol).

[Liquid UV absorber]

TINUVIN213 (manufactured by BASF, melting point -40°C, maximum absorption wavelength 344 nm) (methyl 5-(2-hydroxy-benzotriazol-2-yl)-4-hydroxy-3-tert-butylphenylpropionate)

TINUVIN571 (manufactured by BASF, molecular weight 393.6, melting point -56°C, maximum absorption wavelength 343 nm) (2-(2-hydroxy-benzotriazol-2-yl)-4-methyl-6-dodecylphenol) .

[Triazine UV Absorbers]

TINUVIN1577FF (manufactured by BASF, molecular weight 425, melting point 148°C, maximum absorption wavelength 274 nm) (2-[4,6-diphenyl-1,3,5-triazin-2-yl]-5-(hexyloxy )phenol).

[Benzophenone-based UV absorbers]

CHIMASSORB81/FL (manufactured by BASF, molecular weight: 326.4, melting point: 48 to 49° C.) (2-hydroxy-4-(octyloxy)benzophenone).

[Benzoate-based UV absorbers]

TINUVIN120 (manufactured by BASF, molecular weight 438.7, melting point 192 to 197° C., maximum absorption wavelength 265 nm) (2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate).

[Hindered Amine Stabilizer]

CHIMASSORB2020FDL (manufactured by BASF, molecular weight 2600-3400, melting point 130-136°C) (dibutylamine 1,3,5-triazine N,N-bis(2,2,6,6-tetramethyl-4 -Piperidinyl)-1,6-hexanediamine·N-(2,2,6,6-tetramethyl-4-piperidinyl)butylamine condensation polymer)

CHIMASSORB944FDL (manufactured by BASF, molecular weight 2000-3100, melting point 100-135°C) (poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2 ,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{2,2,6,6-tetramethyl-4-piperidinyl base)imino}])

TINUVIN622LD (manufactured by BASF, molecular weight 3100-4000, melting point 55-70°C) (1-[2-(4-hydroxy-2,2,6,6-tetramethylpiperidine) ethyl succinate])

TINUVIN144 (manufactured by BASF, molecular weight 685, melting point 146-150°C) (2-butyl-2-[3,5-di(tert-butyl)-4-hydroxybenzyl]bis(1,2,2,6 ,6-pentamethyl-4-piperidinyl) malonate

TINUVIN292 (manufactured by BASF, molecular weight 509) (bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate)

TINUVIN770DF (manufactured by BASF, molecular weight 481, melting point 81 to 85° C.) (bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate).

In the present invention, by adding titanium oxide to the thermoplastic elastomer composition, transmission of ultraviolet rays is suppressed, and deterioration due to ultraviolet irradiation can be prevented. In addition, when titanium oxide is added to a thermoplastic elastomer, there is a concern that poor dispersion may degrade durability, so attention should be paid to uniform dispersion during mixing.

<Antioxidants>

In the present invention, an antioxidant is added to the elastomer composition. Antioxidants function as radical scavengers, and mainly prevent deterioration of molecular chains of polymers by scavenging carbon radicals. Antioxidants are exemplified below.

[Hindered phenolic antioxidant]

IRGANOX1010 (manufactured by BASF), Adekastab AO-60 (manufactured by ADEKA Co., Ltd.), Sumiraizer BP-101 (manufactured by Sumitomo Chemical Co., Ltd.) (pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl ) propionate]),

IRGANOX1035 (manufactured by BASF) (2,2-thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]),

IRGANOX1076 (manufactured by BASF) (octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate),

IRGANOX1098 (manufactured by BASF) (N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamide)),

IRGANOX1135 (manufactured by BASF) (isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate),

IRGANOX1330 (manufactured by BASF) (1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene),

IRGANOX1726 (manufactured by BASF) (4,6-bis(dodecylthiomethyl)-o-cresol),

IRGANOX1425 (manufactured by BASF) (bis(3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid monoethyl ester) calcium (50%), polyethylene wax (50%))

IRGANOX1520 (manufactured by BASF) (2,4-bis[(octylthio)methyl]-o-cresol),

IRGANOX245 (manufactured by BASF) (triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] ester),

IRGANOX259 (manufactured by BASF) (1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester),

IRGANOX3114 (manufactured by BASF) (tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate),

IRGANOX5057 (manufactured by BASF) (octylated diphenylamine),

IRGANOX565 (manufactured by BASF) (2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine)

Cyanox CY1790 (manufactured by Sanchemikaru Co., Ltd.) (1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid)

ADEKA STAB AO-40 (manufactured by ADEKA Co., Ltd.), SUMIRAISER BBM (manufactured by Sumitomo Chemical Co., Ltd.) (4,4'-butylenebis(3-methyl-6-tert-butylphenol))

ADEKA STAB AO-50 (manufactured by ADEKA Co., Ltd.), SUMIRAISER BP-76 (manufactured by Sumitomo Chemical Co., Ltd.) (octadecyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate)

ADEKA STAB AO-80 (manufactured by ADEKA Co., Ltd.), SUMIRAISER GA-80 (manufactured by Sumitomo Chemical Co., Ltd.) (3,9-bis[1,1-dimethyl-2-[β-(3-tert-butyl-4 -hydroxy-5-methylphenyl)propanoyl]ethyl]2,4,8,10-tetraoxaspiro[5,5]-undecane).

[Phosphorus antioxidants]

Phosphorus-based antioxidants are used as peroxide decomposing agents, and have good anti-oxidation function during thermal processing, as shown below.

IRGAFOS12 (manufactured by BASF, molecular weight 1462.9) (6,6',6''-[nitrotri(ethyleneoxy)]tris(2,4,8,10-tetra-tert-butylbenzo[d,f] [1,3,2]dioxaphosphapine)),

IRGAFOS38 (manufactured by BASF, molecular weight 514) (bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite),

IRGAFOS168 (manufactured by BASF, molecular weight 646), Adekastab 2112 (manufactured by ADEKA Co., Ltd.), Sumiraizer P-16 (manufactured by Sumitomo Chemical Co., Ltd.) (tris(2,4-di-tert-butylphenyl) phosphite)

アデカスタブPEP-8 (manufactured by ADEKA Co., Ltd.) (distearyl pentaerythritol diphosphite)

ADEKA STAB PEP-36 (manufactured by ADEKA Co., Ltd.) (bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite) (cyliclic neopentante trieribisu (2,6-ji- t-buchiru-4-mechirufeinil) フォスファイト).

[Hydroxyamine series]

IRGASTAB FS042 (manufactured by BASF) (N,N-dioctadecylhydroxylamine).

[Hindered phenol/phosphorus mixed antioxidant]

IRGANOX B225 (manufactured by BASF) (IRGAFOS168:IRGANOX1010=1:1)

IRGANOX215 (manufactured by BASF) (IRGAFOS168:IRGANOX1010=2:1)

IRGANOX220 (manufactured by BASF) (IRGAFOS168:IRGANOX1010=3:1)

IRGANOX921 (manufactured by BASF) (IRGAFOS168:IRGANOX1076=2:1).

[oxygen absorber]

The antioxidant in the present invention is a concept including an oxygen absorbing agent. As the oxygen absorber, a general oxygen absorber capable of capturing oxygen in the air can be used. For example, an iron powder oxygen absorber that absorbs oxygen in the air by the oxidation reaction of iron powder is used. Usually, for a surface area of 0.5 m ² /g or more iron powder 100 parts by mass, combined with 0.1 to 50 parts by mass of metal halides, such as chlorine, bromine, iodine, etc. of alkali metals such as sodium chloride, sodium bromide, calcium chloride, and magnesium chloride or alkaline earth metals of halides. As a mixture of both of them, the surface of the iron powder may be covered with a metal halide. In addition, in the oxygen absorbing agent used in the present invention, porous particles such as zeolite impregnated with water may be combined to further promote the oxidation of iron by the oxygen. In particular, hindered phenolic antioxidants are preferable as the radical scavengers of carbon radicals.

In the present invention, at least one or a combination of two or more of the above-mentioned ultraviolet absorbers and antioxidants can be used. In particular, it is preferable to use a benzotriazole-based ultraviolet absorber and a hindered phenol-based antioxidant in combination. Then, it is preferable to add at least any one of the above-mentioned ultraviolet absorber and antioxidant to the first layer in an amount of 0.5% by mass to 40% by mass of the thermoplastic elastomer component. If the formula ratio is less than 0.5% by mass, the effect expected from adding the above-mentioned ultraviolet absorber or the above-mentioned antioxidant cannot be sufficiently exhibited. In addition, when the proportion of the formula exceeds 40% by mass, the original function of the first layer will be reduced. It is preferable to add at least any one of the above-mentioned ultraviolet absorber and antioxidant in an amount of 2.0% by mass to 20% by mass of the thermoplastic elastomer component.

<Thickness of the first layer>

The thickness of the first layer is 0.05 to 0.6 mm. If the thickness of the first layer is less than 0.05mm, when the polymer laminate composed of the first layer and the second layer is applied to the green tire vulcanization of the inner liner, the first layer may be damaged due to the pressurized pressure, resulting in a tire There are concerns about air leakage. On the other hand, if the thickness of the first layer exceeds 0.6mm, the weight of the tire will increase, and the fuel efficiency will decrease. The thickness of the first layer is more preferably 0.05 to 0.4 mm. For the first layer, a common method for forming a thermoplastic resin or thermoplastic elastomer into a film, such as extrusion molding or calender molding, can be used.

〈2nd floor〉

The second layer is a thermoplastic elastomer composition containing styrene-isoprene-styrene block copolymer (hereinafter also referred to as "SIS") and styrene-isobutylene block copolymer (hereinafter also referred to as "SIB") at least any one.

In addition, the second layer may contain a SIBS modified copolymer, a styrene-based thermoplastic elastomer, or a rubber component. The SIBS modified copolymer is in the range of 5 to 80% by mass, preferably 10 to 80% by mass, of the entire thermoplastic elastomer component. When the SIBS modified copolymer is less than 5% by mass, the vulcanized adhesive force with the first layer may decrease, and if it exceeds 80% by mass, the adhesive force with the carcass may decrease.

Here, the styrene-based thermoplastic elastomer refers to a copolymer containing a styrene block as a hard block. For example, styrene-isoprene-styrene block copolymer (hereinafter also referred to as "SIS"), styrene-isobutylene block copolymer (hereinafter also referred to as "SIB"), styrene-butanediene Styrene-styrene block copolymer (hereinafter also referred to as "SBS"), styrene-isobutylene-styrene block copolymer (hereinafter also referred to as "SIBS"), styrene-ethylene·butylene-styrene block copolymer Segment copolymer (hereinafter also referred to as "SEBS"), styrene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEPS"), styrene-ethylene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEEPS"), styrene-butadiene-butylene-styrene block copolymer (hereinafter also referred to as "SBBS").

In addition, the molecular structure of the styrene-based thermoplastic elastomer may have an epoxy group, and for example, Epofrend A1020 (weight-average molecular weight: 100,000, epoxy equivalent: 500) epoxy group manufactured by Daicel Chemical Industry Co., Ltd. can be used. Modified styrene-butadiene-styrene copolymer (epoxidized SBS).

Since the isoprene block of styrene-isoprene-styrene copolymer (SIS) is a soft block, the polymer film composed of SIS is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film composed of SIS is used for an inner liner, the adhesiveness between the inner liner and a rubber layer such as a carcass is good, so a pneumatic tire with good durability can be obtained.

The molecular weight of the SIS is not particularly limited, but it is preferably 100,000 to 290,000 in weight average molecular weight measured by GPC from the viewpoint of rubber elasticity and formability. If the weight-average molecular weight is less than 100,000, there is a possibility that the tensile strength may decrease, and if it exceeds 290,000, extrusion processability may deteriorate, which is not preferable. The content of the styrene component in the SIS is preferably 10 to 30% by mass in terms of tackiness, cohesiveness, and rubber elasticity.

In the present invention, the degree of polymerization of each block in the SIS is preferably about 500 to 5,000 for isoprene and about 50 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

The SIS can be obtained by a general polymerization method of vinyl compounds, for example, it can be obtained by a living cationic polymerization method. The SIS layer can be obtained by forming the SIS into a film by a common method of forming a thermoplastic resin or thermoplastic elastomer into a film, such as extrusion molding or calender molding.

Since the isobutylene block of styrene-isobutylene block copolymer (SIB) is a soft block, the polymer film composed of SIB is easy to vulcanize and bond with the rubber component. Therefore, when a polymer film composed of SIB is used for an inner liner, the inner liner has good adhesion to, for example, the adjacent rubber forming a carcass or a separator, and thus a pneumatic tire with good durability can be obtained.

As SIB, it is based on the viewpoint of rubber elasticity and adhesiveness. It is preferably linear. The molecular weight of SIB is not particularly limited, but it is preferably 40,000 to 120,000 in weight average molecular weight measured by GPC from the viewpoint of rubber elasticity and formability. If the weight average molecular weight is less than 40,000, the tensile strength may decrease, and if it exceeds 120,000, the extrusion processability may deteriorate, which is not preferable. The content of the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoint of tackiness, cohesiveness, and rubber elasticity. In the present invention, the degree of polymerization of each block in the SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

The SIB can be obtained through the living polymerization method of general vinyl compounds. For example, methylcyclohexane, n-chlorobutane, and cumyl chloride can be added to a mixer, cooled to -70°C, and allowed to react After 2 hours, a large amount of methanol was added to stop the reaction, and vacuum-dried at 60°C to obtain SIB.

The SIB layer can be formed by a common method of forming a SIB into a film of a styrene-based thermoplastic elastomer, such as extrusion molding or calender molding. The thickness of the second layer is preferably 0.01 mm to 0.3 mm. Here, the thickness of the second layer refers to the thickness when, for example, the second layer is composed of only one layer such as an SIS layer or an SIB. On the other hand, when the second layer includes, for example, multiple layers such as an SIS layer and an SIB layer, it refers to their total thickness. If the thickness of the second layer is less than 0.01 mm, when the polymer laminate is applied to the green tire vulcanization of the inner liner, the second layer may be damaged due to the pressurized pressure and the vulcanization adhesive force may decrease. On the other hand, if the thickness of the second layer exceeds 0.3 mm, there is a possibility that the weight of the tire increases and the fuel economy performance decreases. The thickness of the second layer is more preferably 0.05 to 0.2 mm.

In addition, although it is preferable that the second layer is composed of a composite layer of the SIS layer and the SIB layer, between the first layer and the SIS layer, between the first layer and the SIB layer, or between the SIS layer and the SIB layer, it may also be arranged as a second layer. 3-layer film made of urethane rubber and silicone rubber.

<Mixture with SIBS>

In the present invention, the second layer may be composed of a mixture of SIS and SIBS, or a mixture of SIB and SIBS. At this time, the compounding quantity of SIBS is adjusted to the range of 10-80 mass % of a thermoplastic elastomer component, Preferably it is 30-70 mass %. When the SIBS is less than 10% by mass, the adhesion to the first layer tends to decrease, and when the SIBS exceeds 80% by mass, the adhesion to the carcass tends to decrease.

<Tackifier>

In the present invention, at least one of the first layer and the second layer may contain 0.1 to 100 parts by mass of a tackifier relative to 100 parts by mass of the thermoplastic elastomer component. Here, the tackifier refers to a formulating agent for improving the adhesiveness of the thermoplastic elastomer composition, for example, the following tackifiers can be exemplified.

Typical ones are C9 petroleum resin and C5 petroleum resin. Here, C9 petroleum resin is an aromatic petroleum resin, which is obtained by thermally decomposing naphtha to obtain useful compounds such as ethylene, propylene, butadiene, etc. After taking them out, the remaining C5-C9 fractions (mainly C9 fractions) are directly Polymerized in a mixed state. For example, the brand names include Alcon P70, P90, P100, P125, P140, M90, M100, M115, and M135 (all manufactured by Arakawa Chemical Industry Co., Ltd., with a softening point of 70 to 145°C), and Aimarbe S100, S110, P100, P125, P140 (all made by Idemitsu Petrochemical Co., Ltd., aromatic copolymer hydrogenated petroleum resin, softening point 100-140°C, weight-average molecular weight 700-900, bromine value 2.0-6.0g/100g), and Petocol XL (manufactured by Tosoh Corporation).

In addition, C5 petroleum resin is an aliphatic petroleum resin, which is to thermally decompose naphtha to obtain useful compounds such as ethylene, propylene and butadiene. It is obtained by polymerization in a mixed state. As brand names, there are Hiretsu G100 (manufactured by Mitsui Petrochemical Co., Ltd., softening point 100°C), Marukaretsu T100AS (manufactured by Maruzen Oil Co., Ltd., softening point 100°C), and Escoretsu 1102 (manufactured by Tonex Co., Ltd., softening point 110°C).

Terpene resins include, for example, YS Resin PX800N, PX1000, PX1150, PX1250, PXN1150N, Crillon P85, P105, P115, P125, P135, P150, M105, M115, K100 (all manufactured by Yasuhara Chemical Co., Ltd. point 75 ~ 160 ℃).

Aromatic modified terpene resins include, for example, YS resin TO85, TO105, TO115, and TO125 (all manufactured by Yasuhara Chemical Co., Ltd., softening point: 75 to 165° C.) as trade names.

Terpene phenolic resins include, for example, tamanol 803L and 901 (manufactured by Arakawa Chemical Industry Co., Ltd., softening point 120° C. to 160° C.) as trade names, and YS Polyster U115, U130, T80, T100, T115, T145, and T160. (All are manufactured by Yasuhara Chemical Co., Ltd., with a softening point of 75°C to 165°C).

As the coumarone resin, there is, for example, a coumarone resin having a softening point of 90° C. (manufactured by Kobe Oil Chemical Industry Co., Ltd.).

Cougarindene oil has, for example, 15E (manufactured by Kobe Oil Chemical Industry Co., Ltd., pour point: 15° C.) as a trade name.

Rosin esters include, for example, Estelgam AAL, A, AAV, 105, AT, H, HP, HD (all manufactured by Arakawa Chemical Industry Co., Ltd., softening point 68°C to 110°C) as trade names, and Harriester TF, S, C, DS70L, DS90, DS130 (all manufactured by Harima Chemicals Co., Ltd., softening point 68°C to 138°C).

Examples of hydrogenated rosin esters include Super Ester A75, A100, A115, and A125 (all made by Arakawa Chemical Industry Co., Ltd., softening point 70° C. to 130° C.) as trade names.

The alkylphenol resin is, for example, TAMANOL 510 (manufactured by Arakawa Chemical Industry Co., Ltd., softening point: 75° C. to 95° C.) as a trade name.

As a brand name of DCPD, there is Escorech 5300 (manufactured by Tonex Co., Ltd., softening point: 105° C.).

The tackifier can improve the compatibility between the fully hydrogenated petroleum resin of C9 petroleum resin and SIB, without reducing the gas barrier property, and at the same time improve the adhesion. In addition, it also has the effect of lowering the viscosity and can be advantageously used for film extrusion molding.

The tackifier is added in the range of 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass, per 100 parts by mass of the thermoplastic elastomer component of the first layer. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive force with the second layer is insufficient. On the other hand, if it exceeds 100 parts by mass, the adhesiveness is too high, processability and productivity are reduced, and gas barrier properties are also reduced. .

The second layer is arranged between the first layer and the carcass layer on the inner side of the tire, and is required to have adhesion to both. Then, the tackifier is added in the range of 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass, per 100 parts by mass of the thermoplastic elastomer component of the second layer. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive force with the first layer is insufficient. On the other hand, if it exceeds 100 parts by mass, the adhesiveness is too high, the processability and productivity will be reduced, and the gas barrier properties will also be deteriorated. decline.

The thickness of the second layer is adjusted to a range of 0.05 to 0.3 mm. In addition, when the second layer has multiple layers, it is preferable to adjust the total thickness to a range of 0.05 to 0.3 mm.

<Polymer laminate>

In the present invention, a polymer laminate composed of the first layer and the second layer is used for the inner liner. Here, the first layer and the second layer are thermoplastic elastomer compositions, and are in a softened state in the mold at a vulcanization temperature of, for example, 150°C to 180°C. The softened state refers to an intermediate state between solid and liquid with increased molecular mobility. In addition, when the thermoplastic elastomer composition is in a softened state, its reactivity is higher than that in a solid state, so it sticks or adheres to adjacent members. Therefore, in order to prevent the thermoplastic elastomer composition from changing in shape, sticking to adjacent members, and fusing with adjacent members, it is preferable to provide a cooling process at the time of tire manufacture. The cooling step can be performed after the tire is vulcanized, and then rapidly cooled to 50-120° C. for 10 to 300 seconds to cool the inside of the bladder. As the cooling medium, one or more selected from the group consisting of air, water vapor, water, and oil is used. By adopting this cooling step, it is easy to form a thin inner liner in the range of 0.05 to 0.6 mm.

Next, Fig. 2 shows the arrangement state of the inner liner and the ply in the vulcanized tire. In FIG. 2 , polymer laminate PL is composed of SIBS layer or SIBS-modified copolymer layer PL1 as the first layer, and SIS layer PL2 as the second layer. When this polymer laminate PL is applied to the inner liner of a pneumatic tire, if the SIS layer PL2 is placed in contact with the carcass layer 6 and placed outward in the radial direction of the tire, in the vulcanization process of the tire, the bond between the SIS layer PL2 and the tire can be improved. Body 61 adhesive strength. Therefore, the inner liner of the obtained pneumatic tire adheres well to the rubber layer of the carcass 6, and thus can have good air permeation resistance and durability.

In FIG. 3 , polymer laminate PL is composed of SIBS layer or SIBS-modified copolymer layer PL1 as the first layer, and SIB layer PL3 as the second layer. When this polymer laminate PL is applied to the inner liner of a pneumatic tire, if the surface of the SIB layer PL3 is in contact with the carcass layer 6 and is arranged outward in the radial direction of the tire, the SIB layer PL3 can be improved in the vulcanization process of the tire. Bonding strength with the carcass 61. Therefore, the inner liner of the obtained pneumatic tire adheres well to the rubber layer of the carcass 6, and thus can have good air permeation resistance and durability.

In FIG. 4 , polymer laminate PL is formed by laminating SIBS layer or SIBS-modified copolymer layer PL1 as the first layer, SIS layer PL2 and SIB layer PL3 as the second layer in this order. When this polymer laminate PL is applied to the inner liner of a pneumatic tire, if the surface of the SIB layer PL3 is in contact with the carcass layer 6 and is arranged outward in the radial direction of the tire, the SIB layer PL3 can be improved in the vulcanization process of the tire. Adhesion strength to ply 6. Therefore, the inner liner of the obtained pneumatic tire adheres well to the rubber layer of the carcass 6, and thus can have good air permeation resistance and durability.

In FIG. 5 , polymer laminate PL is formed by laminating SIBS layer or SIBS-modified copolymer layer PL1 as the first layer, SIB layer PL3 and SIS layer PL2 as the second layer in this order. When this polymer laminate PL is applied to the inner liner of a pneumatic tire, if the surface of the SIS layer PL2 is in contact with the carcass layer 6 and is arranged outward in the radial direction of the tire, the SIS layer PL2 can be improved in the vulcanization process of the tire. Adhesion strength to ply 6. Therefore, the inner liner adheres well to the rubber layer of the carcass 6 , and thus can have good air permeation resistance and durability.

<Manufacturing method of pneumatic tire>

The pneumatic tire of the present invention can be produced by a general production method. First, an inner liner is produced using the polymer laminate PL. The pneumatic tire 1 can be produced by applying the inner liner to a green tire and co-vulcanizing and molding other components. When disposing the polymer laminate PL on a green tire, the SIS layer PL2 or the SIB layer PL3 which is the second layer of the polymer laminate PL is arranged outward in the radial direction of the tire in contact with the carcass layer 6 . With such an arrangement, the adhesive strength between the SIS layer PL2 or the SIB layer PL3 and the carcass 61 can be increased in the tire vulcanization step. The inner liner of the obtained pneumatic tire adheres well to the rubber layer of the carcass 6, and thus can have good air permeability resistance and durability.

Example

<Polymer laminate>

The thermoplastic elastomer (SIB, SIBS, SIS, and SIBS-modified copolymer), ultraviolet absorber, and antioxidant used in the production of the polymer laminate composed of the first layer and the second layer of the present invention are adjusted as follows.

[SIB]

Into a 2L reaction vessel equipped with a stirrer, add 589 mL of methylcyclohexane (dried through molecular sieves), 613 mL of n-chlorobutane (dried through molecular sieves), and 0.550 g of cumyl chloride. After cooling the reaction container to -70°C, 0.35 mL of α-picoline (2-picoline) and 179 mL of isobutene were added. Further, 9.4 mL of titanium tetrachloride was added to start polymerization, and the solution was reacted at -70°C for 2.0 hours while stirring the solution. Next, 59 mL of styrene was added to the reaction container, and after continuing the reaction for 60 minutes, a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed with water twice. The toluene solution was added to the methanol mixture to precipitate the polymer, and the obtained polymer was dried at 60° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer (styrene component content: 15% by mass, weight average Molecular weight: 70,000).

[SIBS]

"Sibstar SIBSTAR 102T (Shore A hardness: 25, styrene component content: 25 mass %, weight average molecular weight: 100,000)" manufactured by Kaneka Co., Ltd. was used.

[SIS]

D1161JP (styrene component content: 15% by mass, weight average molecular weight: 150,000) manufactured by Clayton Polymer Co., Ltd. was used.

[Manufacture of SIBS modified copolymer]

75 g of a styrene-isobutylene block copolymer (30% styrene content, 0.216 moles of styrene units) was placed in a 2 L separation bottle, and the inside of the container was replaced with nitrogen. Using a syringe, 1200 mL of n-hexane dried over molecular sieves and 1800 mL of n-butyl chloride dried over molecular sieves were added.

Then, 30 g (0.291 mol) of methacryloyl chloride was added using a syringe. Then, while stirring the solution, 39.4 g (0.295 mol) of aluminum trichloride was added to start the reaction. After reacting for 30 minutes, about 1000 mL of water was added to the reaction solution and vigorously stirred to complete the reaction. Wash the reaction solution several times with a large amount of water, then slowly drop a large amount of methanol and acetone mixed solvent (1:1) to precipitate the reaction product, and then dry the reaction product under vacuum at 60°C for 24 hours to obtain SIBS Modified copolymer (weight average molecular weight: 150,000, styrene content: 20% by weight, acid chloride: 1.0% by weight).

[ultraviolet absorber]

As a benzotriazole-based ultraviolet absorber manufactured by ADEKA Co., Ltd., "Adecastab LA-36" (2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5 -chlorobenzotriazole). The melting point of the ultraviolet absorber is 138-141° C., the molecular weight is 315.8, and the maximum absorption wavelength is 353 nm.

[Antioxidants]

As the hindered phenolic antioxidant manufactured by BASF Corporation, "IRGANOX 1010" (pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]) was used. The melting point of the antioxidant is 110-125° C., the specific gravity is 1.15, and the molecular weight is 117.7.

(Note 1) Tackifier: C9 petroleum resin, Alcon P140 (manufactured by Arakawa Chemical Industry Co., Ltd., softening point 140° C., weight average molecular weight Mw: 900).

(Note 2) Polyisobutylene: manufactured by Nippon Oil Corporation, "Tetrax 3T" (viscosity average molecular weight 30,000, weight average molecular weight 49,000).

<Manufacturing method of inner liner>

，L/D：30，机筒温度：220℃）颗粒化。然后，通过T型模头挤压机（螺杆直径：，L/D：50，模具宽度：500mm，机筒温度：220℃，薄膜尺度：第1层为0.25mm，第2a层及第2b层均为0.05mm）制作气密层。According to the implementation formula of table 1, table 2, comparison formula, the thermoplastic elastomer composition of SIBS modified copolymer, SIBS, SIS and SIB etc. is passed through biaxial extruder (screw diameter:

, L/D: 30, barrel temperature: 220°C) granulation. Then, through a T-die extruder (screw diameter: , L/D: 50, mold width: 500mm, barrel temperature: 220°C, film size: 0.25mm for the first layer, 0.05mm for both the 2a layer and the 2b layer) to make the airtight layer.

<Manufacturing of pneumatic tires>

Pneumatic tires were produced in a size 195/65R15 having the basic configuration shown in FIG. 1 . The above-mentioned polymer laminate was used as an inner liner to manufacture a green tire, and press vulcanization was performed at 170° C. for 20 minutes. The vulcanized tire was not taken out from the vulcanization mold, but was cooled at 110° C. for 3 minutes, and then taken out from the vulcanization mold. As cooling medium, water is used.

Table 1 describes comparative formulations 1-6 and implementation formulations 1-8 of the first layer, and Table 2 describes the contents of comparison formulations 7-13 and implementation formulations 9-17 of the second layer. Tires of Examples and Comparative Examples were produced using these formulations for the first layer and the second layer. The specifications and performance evaluation results are shown in Tables 3 to 4.

<Comparative examples 1 to 10>

Comparative Examples 1 to 3 are examples of inner liners in which SIBS is used for the first layer and SIS is used for the second layer. Comparative Example 4 is an example of an inner liner in which a SIBS modified copolymer is used for the first layer and SIS is used for the second layer. Comparative Examples 5 and 6 are examples of inner liners in which a mixture of SIBS and a SIBS-modified copolymer is used for the first layer and SIS is used for the second layer. Comparative Example 7 is an example of an inner liner of a composite layer using SIBS as the first layer and a composite layer of SIS (layer 2a) and SIB (layer 2b) as the second layer.

Comparative Examples 8 and 9 are examples of inner liners based on formulations using SIBS for the first layer and a mixture of SIS and SIBS for the second layer. Comparative Example 10 is an example of an inner liner in which SIBS is used for the first layer and SIS, SIBS, and a SIBS-modified copolymer are used for the second a layer.

<Examples 1 to 12>

It is an example in which either one of the ultraviolet absorber and the antioxidant, or both, are mixed in the first layer and the second layer in an amount of 0.5 to 40% by mass with respect to 100% by mass of the thermoplastic elastomer.

Examples 1 to 5 are examples of inner liners using SIBS for the first layer and SIS for the second layer. Example 6 is an example of an inner liner in which a SIBS modified copolymer is used for the first layer and SIS is used for the second layer. Examples 7 and 8 are examples of inner liners in which a mixture of SIBS and a SIBS-modified copolymer is used for the first layer and SIS is used for the second layer.

Example 9 is an example of an inner liner using SIBS for the first layer, SIS for the 2a layer, and SIB for the 2b layer. Examples 10 and 11 are examples of inner liners in which SIBS is used for the first layer and a mixture of SIS and SIBS is used for the second layer. Example 12 is an example of an inner liner using SIBS for the first layer and a mixture of SIS, SIBS, and a SIBS-modified copolymer for the second layer. It has been confirmed that the examples of the present invention have improved weather resistance index, flex crack growth index, and elastic modulus change index compared with the comparative examples.

Example 1 and Example 2 are examples in which the compounding quantity of the antioxidant of the 1st layer was changed. In addition, Example 3 and Example 4 are examples in which the compounding quantity of the ultraviolet absorber of the 1st layer was changed. In addition, Example 5 is an example in which 0.5% by mass of an antioxidant and an ultraviolet absorber were added to both the first layer and the second layer.

〈Performance test〉

With regard to the pneumatic tires manufactured as above, the following performance tests were performed.

〈Weather Resistance Test〉

The interior of the inner liner was subjected to a weather resistance test under the following conditions using a sunlight-type carbon arc lamp weather resistance tester manufactured by Suga Testing Instrument Co., Ltd. The number of cracks in the airtight layer after the test was obtained by irradiating for 60 hours under the conditions of a tank temperature of 63°C, a humidity of 50%, 60°C, and 12 minutes of rain. Based on Comparative Example 1, the relative value of the number of cracks with other Comparative Examples and Examples was obtained, and the weather resistance index was calculated from the following formula. The larger the numerical value, the better the weather resistance.

Weather resistance index=(the number of cracks in Comparative Example 1)/(the number of cracks in each example)×100.

<Flex crack growth test>

The endurance running test evaluated whether the inner liner was cracked or peeled off. The trial tire was installed on the JIS standard rim 15×6JJ, the internal pressure of the tire was set to 150KPa, which was lower than the normal internal pressure, the load was 600kg, the speed was 100km/h, and the inside of the tire was observed when the driving distance was 20,000km, and the cracks, The amount of stripping. Based on Comparative Example 1, the crack growth properties of the respective Comparative Examples and Examples are represented by indices. Larger index values indicate less flex crack growth.

Flexural crack growth index=(the number of cracks in Comparative Example 1)/(the number of cracks in each example)×100.

<Elastic modulus change index>

Under the same conditions as the flex crack growth test, the inner liner of the pneumatic tire before driving and after driving 20,000 km was evaluated using a viscoelasticity spectrometer VES (Iwamoto Manufacturing Co., Ltd.) at a temperature of 70°C and the initial strain The rate of increase of the dynamic elastic modulus (E') under the conditions of 10% and 2% dynamic strain.

Using Comparative Example 1 as a reference, the elastic modulus change index was obtained as a relative value to the value of the dynamic elastic modulus (E') of each Comparative Example and Example. The larger the index value, the smaller the increase rate of the modulus of elasticity, which is good.

Change rate of elastic modulus = (elastic modulus after driving) / (elastic modulus before driving) × 100

Elastic modulus change index=(change rate of elastic modulus of Comparative Example 1)/(change rate of elastic modulus of each example)×100.

<Durability Driving Test>

The endurance running test measures the running distance until the tire is damaged under the injection of oxygen. Place the trial tire in an atmosphere of 90% oxygen and 70% relative humidity for 336 hours, then assemble the rim, inject 100% oxygen, and place it in an atmosphere of 350kPa internal pressure, 90% oxygen, and 70% relative humidity for 336 hours. Then, it was mounted on a JIS standard rim 15×6JJ, injected with 100% oxygen, and the internal pressure of the tire was set at 280kPa to prepare the tire.

The driving condition is to start driving with a load of 500kg and a speed of 170km/h, test drive for 10 minutes, then cool down, start driving from 170km/h, increase the speed by 10km/h every 20 minutes, and measure the driving speed until the tire fails.

The running distance at the time of failure of each comparative example and embodiment was obtained, and the relative value index thereof was obtained with comparative example 1 as a reference. The larger the index value, the faster and better the durability driving speed.

Endurance running speed index=(traveling speed of each embodiment at failure)/(traveling speed of comparative example 1 at failure)×100.

<Comprehensive judgment>

Judgment A means that all of the following conditions are satisfied.

(a) The weather resistance index is above 100

(b) The flex crack growth index is above 100

(c) The elastic modulus change index is above 100

(d) Durable driving speed index greater than 100.

Judgment B means that any one of the following conditions is satisfied. When multiple judgments are made, the one with the lowest evaluation is used.

(a) The weather resistance index is below 100

(b) The flex crack growth index is below 100

(c) The elastic modulus change index is below 100

(d) Durable driving speed index greater than 100.

Claims (5)

1. an air-inflation tyre (1), it possesses and has air-retaining liner (9) in the tire inner side that is set up in the carcass plies (6) between pair of bead portion (4), it is characterized in that,

Described air-retaining liner (9) is by being configured in the 1st layer (PL1) of tire inner side and forming with join the 2nd layer (PL2, PL3) of configuration of the rubber layer of described carcass plies (6);

Described the 1st layer (PL1) is composition for thermoplastic elastomer, this composition for thermoplastic elastomer contains thermoplastic elastomer, and in ultraviolet absorbent and antioxidant at least any one, described thermoplastic elastomer contain styrene-isobutylene-styrene block copolymer and styrene block thereof part had in the acyl chlorides of dangling bond or anhydride modified SIBS modified copolymer at least any one;

Described the 2nd layer (PL2, PL3) is composition for thermoplastic elastomer, this composition for thermoplastic elastomer contain in SIS and styrene-isobutylene block copolymer at least any one.

2. air-inflation tyre according to claim 1 (1), in described the 1st layer (PL1), be mixed with in the ultraviolet absorbent of 0.5 quality %～40 quality % of thermoplastic elastomer composition and antioxidant at least any one.

3. air-inflation tyre according to claim 1 (1), in the composition for thermoplastic elastomer of any one in described the 1st layer (PL1) and described the 2nd layer (PL2, PL3), be mixed with the SIBS modified copolymer of 5 quality %～100 quality % of thermoplastic elastomer composition.

4. air-inflation tyre according to claim 1 (1), wherein, the composition for thermoplastic elastomer of described the 1st layer (PL1) is the compound of styrene-isobutylene-styrene block copolymer and SIBS modified copolymer.

5. air-inflation tyre according to claim 1 (1), in the composition for thermoplastic elastomer of any one in described the 1st layer (PL1) and described the 2nd layer (PL2, PL3), is mixed with tackifier.

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